Chapter 21: The Genetic Basis of Development

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Chapter 21 The Genetic Basis of Development

• From single cell to multicellular organisms
• Embryonic development involves cell division,
  morphogenesis, and cell differentiation
• Researchers study development in model organisms
  (fruit flies, nematodes) to identify general
  priciples
• Differential gene expression
• Different types of cells in an organism have the
  same DNA
• Different cell types make different proteins,
  usually as a result of transcriptional regulation
• Transcriptional regulation is directed by
  maternal molecules in the cytoplasm and signals
  from other cells

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Chapter 21 The Genetic Basis of Development
continued

• Genetic and Cellular Mechanisms of pattern
  formation
• Genetic analysis of development in Drosophila
  reveals how genes control development
• Gradients of maternal molecules in the early
  embryo control axis formation
• A cascade of gene activations sets up the
  segmentation pattern in Drosophila
• Homeotic genes direct the identity of body parts
• Homeobox genes have been highly conserved in
  evolution
• Neighboring cells instruct other cells to form
  particular structures cell signaling and
  induction in the nematode
• Plant development depends on cell signaling and
  transcriptional regulation

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Pudgy Mouse
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Stargazer
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Chapter 21 The Genetic Basis of Development

• From single cell to multicellular organisms
• Embryonic development involves cell division,
  morphogenesis, and cell differentiation
• Researchers study development in model organisms
  (fruit flies, nematodes) to identify general
  priciples
• Differential gene expression
• Different types of cells in an organism have the
  same DNA
• Different cell types make different proteins,
  usually as a result of transcriptional regulation
• Transcriptional regulation is directed by
  maternal molecules in the cytoplasm and signals
  from other cells

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Chapter 21 The Genetic Basis of Development
continued

• Genetic and Cellular Mechanisms of pattern
  formation
• Genetic analysis of development in Drosophila
  reveals how genes control development
• Gradients of maternal molecules in the early
  embryo control axis formation
• A cascade of gene activations sets up the
  segmentation pattern in Drosophila
• Homeotic genes direct the identity of body parts
• Homeobox genes have been highly conserved in
  evolution
• Neighboring cells instruct other cells to form
  particular structures cell signaling and
  induction in the nematode
• Plant development depends on cell signaling and
  transcriptional regulation

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Mendel and the Gene Idea

• Gregor Mendels Discoveries
• Mendel brought and experimental and quantitative
  approach to genetics
• By the law of segregation, the two alleles for a
  character a packed into separate gametes
• By the law of independent assortment, each pair
  of alleles segregates into gametes independantly
• Mendelian inheritance reflects rules of
  probability
• Mendel discovered the particulate behavior of
  genes

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Mendel and the Gene Idea continued

• Extending Mendelian Genetics
• The relationship between genotype and phenotype
  is rarely simple
• Mendelian Inheritance in Humans
• Pedigree analysis reveals Mendelian patterns in
  human inheritance
• Many human disorders follow Mendelian patterns of
  inheritance
• Technology is providing new tools for genetic
  testing and counseling

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Mendel and the Gene Idea

• Gregor Mendels Discoveries
• Mendel brought and experimental and quantitative
  approach to genetics
• By the law of segregation, the two alleles for a
  character a packed into separate gametes
• By the law of independent assortment, each pair
  of alleles segregates into gametes independantly
• Mendelian inheritance reflects rules of
  probability
• Mendel discovered the particulate behavior of
  genes

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Mendel and the Gene Idea continued

• Extending Mendelian Genetics
• The relationship between genotype and phenotype
  is rarely simple
• Mendelian Inheritance in Humans
• Pedigree analysis reveals Mendelian patterns in
  human inheritance
• Many human disorders follow Mendelian patterns of
  inheritance
• Technology is providing new tools for genetic
  testing and counseling

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The Chromosomal Basis of Inheritance

• Relating Mendelism to Chromosomes
• Mendelian inheritance has its physical basis in
  the behavior of chromosomes during sexual life
  cycles
• Thomas Hunt Morgan traced a gene to a specific
  chromosome on fruit flies
• Linked genes tend to be inherited together
  because they are located on the same chromosome
• Independent assortment of chromosomes and
  crossing over produce genetic recombinants
• Geneticists can use recombination data to map a
  chromosomes genetic loci

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The Chromosomal Basis of Inheritance continued

• Sex Chromosomes
• The chromosomal basis of sex varies with the
  organism
• Sex-linked genes have unique patterns of
  inheritance
• Errors and Exceptions to Chromosomal Inheritance
• Alterations of chromosome number or structure
  cause some genetic disorders
• The phenotypic effects of some genes depend on
  whether they were inherited from the mother or
  father
• Extranuclear genes exhibit a non-Mendelian
  pattern of inheritance

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Calico Cat
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Viscacha Rat
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Cytoplasmic Inheritance
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Traslocation
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The Chromosomal Basis of Inheritance

• Relating Mendelism to Chromosomes
• Mendelian inheritance has its physical basis in
  the behavior of chromosomes during sexual life
  cycles
• Thomas Hunt Morgan traced a gene to a specific
  chromosome on fruit flies
• Linked genes tend to be inherited together
  because they are located on the same chromosome
• Independent assortment of chromosomes and
  crossing over produce genetic recombinants
• Geneticists can use recombination data to map a
  chromosomes genetic loci

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The Chromosomal Basis of Inheritance continued

• Sex Chromosomes
• The chromosomal basis of sex varies with the
  organism
• Sex-linked genes have unique patterns of
  inheritance
• Errors and Exceptions to Chromosomal Inheritance
• Alterations of chromosome number or structure
  cause some genetic disorders
• The phenotypic effects of some genes depend on
  whether they were inherited from the mother or
  father
• Extranuclear genes exhibit a non-Mendelian
  pattern of inheritance